Low dielectric constant fluorine and carbon-containing silicon oxide dielectric material characterized by improved resistance to oxidation

ABSTRACT

A process is provided for forming a low k fluorine and carbon-containing silicon oxide dielectric material by reacting with an oxidizing agent one or more silanes including one or more organofluoro silanes characterized by the absence of aliphatic C—H bonds. In one embodiment, the process is carried out using a mild oxidizing agent. Also provided is a low dielectric constant fluorine and carbon-containing silicon oxide dielectric material for use in an integrated circuit structure containing silicon atoms bonded to oxygen atoms, silicon atoms bonded to carbon atoms, and carbon atoms bonded to fluorine atoms, where the dielectric material is characterized by the absence of aliphatic C—H bonds and where the dielectric material has a ratio of carbon atoms to silicon atoms of C:Si greater than about 1:3.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The subject matter of this application relates to the subjectmatter of copending application docket number 00-446, entitled “APROCESS FOR FORMING A LOW DIELECTRIC CONSTANT FLUORINE ANDCARBON-CONTAINING SILICON OXIDE DIELECTRIC MATERIAL CHARACTERIZED BYIMPROVED RESISTANCE TO OXIDATION”, assigned to the assignee of thisapplication, and filed on the same date as this application.

[0002] The subject matter of this application relates to the subjectmatter of copending application docket number 00-643, entitled “APROCESS FOR FORMING A LOW DIELECTRIC CONSTANT FLUORINE ANDCARBON-CONTAINING SILICON OXIDE DIELECTRIC MATERIAL CHARACTERIZED BYIMPROVED RESISTANCE TO OXIDATION”, assigned to the assignee of thisapplication, and filed on the same date as this application.

[0003] The subject matter of this application relates to the subjectmatter of copending U.S. patent application Ser. No. 09/590,310, filedon Jun. 7, 2000, entitled “A LOW TEMPERATURE PROCESS FOR FORMING A LOWDIELECTRIC CONSTANT FLUORINE AND CARBON-CONTAINING SILICON OXIDEDIELECTRIC MATERIAL CHARACTERIZED BY IMPROVED RESISTANCE TO OXIDATIONAND GOOD GAP-FILLING CAPABILITIES”, and assigned to the assignee of thisapplication.

BACKGROUND OF THE INVENTION

[0004] 1. Field of the Invention

[0005] This invention relates to integrated circuit structures. Moreparticularly this invention relates to the low temperature formation ofa low dielectric constant (k) fluorine and carbon-containing siliconoxide dielectric material for use in the formation of integrated circuitstructures.

[0006] 2. Description of the Related Art

[0007] The shrinking of integrated circuits has resulted in levels ofelectrically conductive interconnects being placed closer togethervertically, as well as reduction of the horizontal spacing between theelectrically conductive interconnects, such as metal lines, on anyparticular level of such interconnects. As a result, capacitance hasincreased between such conductive portions, resulting in loss of speedand increased cross-talk. One proposed approach to solving this problemof high capacitance is to replace the conventional silicon oxide (SiO₂)dielectric material, having a dielectric constant (k) of about 4.0, withanother insulation material having a lower dielectric constant tothereby lower the capacitance.

[0008] Dobson et al., in an article entitled “Advanced SiO₂Planarization Using Silane and H₂O₂”, published in SemiconductorInternational, December 1994, at pages 85-88, describe the lowtemperature formation of SiO₂ by reaction of silane (SiH₄) with hydrogenperoxide (H₂O₂) to produce a silicon oxide which flows like a liquid andthus exhibits good gap fill characteristics.

[0009] In an article by L. Peters, entitled “Pursuing the Perfect Low-KDielectric”, published in Semiconductor International, Volume 21, No.10, September 1998, at pages 64-74, a number of alternate dielectricmaterials are disclosed and discussed. Included in these dielectricmaterials is a description of a low k dielectric material having adielectric constant of about 3.0 formed using a Flowfill chemical vapordeposition (CVD) process developed by Trikon Technologies of Newport,Gwent, U.K. The process is said to react methyl silane (CH₃—SiH₃) withhydrogen peroxide (H₂O₂) to form monosilicic acid which condenses on acool wafer and is converted into an amorphous methyl-doped silicon oxidewhich is annealed at 400° C. to remove moisture. The article goes on tostate that beyond methyl silane, studies show a possible k of 2.75 usingdimethyl silane in the Flowfill process.

[0010] An article by S. McClatchie et al. entitled “Low DielectricConstant Oxide Films Deposited Using CVD Techniques”, published in the1998 Proceedings of the Fourth International Dielectrics For ULSIMultilevel Interconnection Conference (Dumic) held on Feb. 16-17, 1998at Santa Clara, Calif., at pages 311-318, also describes the formationof methyl-doped silicon oxide by the low-k Flowfill process of reactingmethyl silane with H₂O₂ to achieve a dielectric constant of ˜2.9.

[0011] The incorporation of such carbon-doped silicon oxide dielectricmaterial into interconnect architecture has been very attractive notonly because of the low k properties, but also because of thecompatibility with conventional silicon process technologies. Generallythese materials remain stable upon annealing at temperatures of up to500° C. The carbon doped silicon oxide materials are characterized bythe structure of amorphous silicon oxide with incorporated methyl groupsand hydrogen species, and are also characterized by a reduced density incomparison with conventional silicon oxide that can be explained by theformation of microporosity surrounding the incorporated methyl groups.Furthermore, such hydrocarbon-modified silicon oxide dielectricmaterials deposited by CVD techniques are also characterized by strongadhesion.

[0012] While such carbon-doped silicon oxide dielectric materials doexhibit the desired low k (i.e., dielectric constants below about 3.0),resulting in reduced capacitance of the dielectric material, a majorproblem of such carbon-doped silicon oxide is a low resistance tooxidation that results in a destruction of the incorporated hydrocarbonsand a resulting increase in the overall dielectric constant of thedielectric material. The sensitivity to oxidation is thought to be dueto the reactivity of the C—H bonds of the methyl group bonded tosilicon. The removal of the methyl group results in a more hydrophilicsurface that may be responsible for a so-called “via poisoning” which isobserved after via etch and photoresist strip with oxygen-containingplasma, and is related to suppression of the surface nucleation insubsequent via liner deposition steps.

[0013] More recently, Sugahara et al., in an article entitled “ChemicalVapor Deposition of CF₃-Incorporated Silica Films for InterlayerDielectric Applications”, published in the 1999 Joint InternationalMeeting, Electrochemical Society Meeting Abstracts, volume 99-2,Abstract 746, 1999, described the reaction oftrimethyl-fluoromethyl-silane (CF₃Si(CH₃)₃) with an ozone oxidizer at anelevated temperature. Sugahara et al. stated that the low reactivity ofSi—alkyl bonds required the deposition to be carried at elevatedtemperatures (˜350° C.). The material demonstrated resistance tooxidation by oxygen plasma. However, it is known that dielectric filmsproduced by high temperature ozone processes are characterized by poorgap-fill, while continuous shrinkage in feature size of integratedcircuit structure demands an increased gap-fill capability. Further, thepresence of C—H bonds in the compound used by Sugahara may yieldoxidation-sensitive dielectric materials due to the presence of C—Hbonds in the precursor silane compound.

[0014] It would, therefore, be desirable to provide a low k siliconoxide dielectric material which exhibits properties of better resistanceto oxidation during deposition and subsequent processing steps. It wouldalso be desirable to provide, in at least one embodiment, a low ksilicon oxide dielectric material which exhibits the gap-fill propertiesand film adherence properties of CVD-formed low k carbon doped siliconoxide dielectric materials such as discussed by the Dobson et al.,Peters, and McClatchie et al. articles discussed above, while alsomaintaining a low formation temperature to conserve the thermal budgetof the integrated circuit structure. This invention provides thesecharacteristics and provides additional advantages as well.

SUMMARY OF THE INVENTION

[0015] The invention provides a process for forming a low k fluorine andcarbon-containing silicon oxide dielectric material by reacting with anoxidizing agent one or more silanes including one or more organofluorosilanes characterized by the absence of aliphatic C—H bonds. In oneembodiment of the invention, the oxidizing agent is a mild oxidizingagent.

[0016] The invention further provides a low dielectric constant fluorineand carbon-containing silicon oxide dielectric material for use in anintegrated circuit structure containing silicon atoms bonded to oxygenatoms, silicon atoms bonded to carbon atoms, and carbon atoms bonded tofluorine atoms, where the dielectric material is characterized by theabsence of aliphatic C—H bonds and where the dielectric material has aratio of carbon atoms to silicon atoms of C:Si greater than about 1:3.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The sole drawing is a flowsheet illustrating one embodiment ofthe process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The invention provides a process for forming a low dielectricconstant (k) fluorine and carbon-containing silicon oxide dielectricmaterial which includes reacting with an oxidizing agent one or moresilanes including one or more organofluoro silanes characterized by theabsence of aliphatic C—H bonds.

[0019] The low k fluorine and carbon-containing silicon oxide dielectricmaterial formed in the method of the invention will have a resultant lowdielectric constant relative to silicon oxide or silicon nitridedielectric materials, and will have an increased resistance to oxidationrelative to organo-containing silicon oxide dielectric materials, whichcontain oxidant-sensitive aliphatic C—H bonds.

[0020] As used herein, an “organofluoro silane” is a compound thatcontains at least one silicon atom bonded to at least one carbon atom,at least one carbon atom bonded to at least one fluorine atom, and,optionally, one or more silicon atoms bonded to at least one hydrogenatom.

[0021] Use herein of the term “silanes” refers to silicon-containingcompounds containing at least one silicon atom bonded to at least onehydrogen atom or bonded to at least one carbon atom. Exemplary silanesinclude SiH₄, SiH₃(CH₃), and SiH₃(CF₃).

[0022] The term “aliphatic C—H bond” refers to a C—H bond where thecarbon atom bonded to the hydrogen atom is not in an aromatic ring;thus, “aliphatic C—H bond”, as used herein, includes alicyclic C—Hbonds. Similarly, an “aliphatic hydrogen” is a hydrogen atom bound to acarbon through an aliphatic C—H bond.

[0023] By use of the interchangeable terms “low k” or “low dielectricconstant” herein is meant a dielectric constant below the dielectricconstant of silicon oxide or silicon nitride. Preferably, a lowdielectric constant is a dielectric constant below about 3.5, and morepreferably below about 3.

[0024] The term “oxidizing agent” refers to an oxygen-containingcompound capable of reacting with an organofluoro silane to form one ormore Si—O bonds. Exemplary oxidizing agents include hydrogen peroxide,ozone (O₃), oxygen (O₂), oxides of nitrogen (N₂O, NO, NO₂), and mixturesthereof.

[0025] By use of the term “mild oxidizing agent” is meant an oxidizingagent, such as a peroxide, capable of oxidizing an organofluoro silanereactant at a low temperature, and which will not oxidize sufficientlyvigorously to cause the Si—C bonds to break in preference to Si—H bonds,since cleavage of Si—C bonds can interfere with the film-formingcapabilities of the reaction product. Typically, a mild oxidizing agentwill cause cleavage of Si—H bonds in preference to Si—C bonds. Anexemplary mild oxidation agent is hydrogen peroxide.

[0026] The term “strong oxidizing agent” means an oxidizing agentcapable of forming Si—O bonds more readily than hydrogen peroxide.Exemplary strong oxidizing agents include ozone (O₃), oxygen (O₂),oxides of nitrogen (N₂O, NO, NO₂), and mixtures thereof.

[0027] The term “silicon-bonded moiety” as used herein refers to an atomor group of atoms, containing at least one atom bonded to a siliconatom.

[0028] By use of the term “low temperature” is meant a temperature notexceeding about 25° C., preferably not exceeding about 10° C., and mostpreferably not exceeding about 5° C. Typically, this temperature will bemeasured by reference to the temperature of the substrate support.

[0029] Organofluoro Silane

[0030] In one embodiment of the invention, at least one silicon atom ofthe organofluoro silane is bonded to at least one hydrogen atom.Reacting such an organofluoro silane with an oxidizing agent causescleavage of Si—H bonds and formation of one Si—O bond for each Si—H bondcleaved. Other moieties that can be bonded to each silicon atom include:oxygen atoms bonded to either another silicon atom or a carbon atom; ororganofluoro moieties containing carbon atoms bonded to fluorine atomsbut not containing aliphatic C—H bonds; or both. By not containingaliphatic C—H bonds, the fluorine and carbon-containing moiety is lesssusceptible to oxidation by the oxidizing agent when the organofluorosilane is reacted with the oxidizing agent. An organofluoro silanecharacterized by the lack of aliphatic C—H bonds will preferably containat least one hydrogen atom bound to a silicon atom and at least onecarbon atom bound to a silicon atom. Exemplary organofluoro silaneswhich may be used in the method of the invention include (H)₃Si(CF₃),(H)₃Si(CF₂CF₃), (H)₃Si(CF(CF₃)₂), (H)₃Si(C(CF₃)₃), (H)₃Si(CF₂)Si(H)₃,(H)₃Si(CF₂)Si(CF₃)(H)₂, (H)₂(CF₃)Si(CF₂)Si(CF₃)(H)₂, ((CF₃)(H)SiO)₄, and((CF)₃(H)Si(CF₂))₄.

[0031] At least one silicon-bonded moiety will contain at least onecarbon atom bound to one or more fluorine atoms. Typically, this carbonand fluorine-containing moiety will be a saturated fluorocarboncontaining only carbon atoms and fluorine atoms and having the generalformula C_(x)F_(2x+1), where x ranges from 1 to 5; for example, —CF₃,—CF₂CF₃, —CF(CF₃)₂, —CF₂CF₂CF₃, —CF₂CF₂CF₂CF₃, —CF₂CF(CF₃)₂, and—C(CF)₃, and the like. While x can range from 1 to 5, x preferablyranges from 1 to 4, more preferably ranges from 1 to 3, most preferablyranges from 1 to 2, and typically is 1. An organofluoro silane havingsuch a silicon-bonded organofluoro moiety will typically also contain ahydrogen atom bonded to a silicon atom. In one embodiment, anorganofluoro silane will contain only: one or more silicon atoms; one ormore carbon atoms; one or more fluorine atoms; one or more hydrogenatoms, where the hydrogen atoms are bonded only to silicon atoms; and,optionally, one or more oxygen atoms.

[0032] An example of a family of such compounds has the general formulafor single-silicon atom-containing compounds:(H)_(y)Si(C_(x)F_(2x+1))_(4−y), where y is 1 to 3 and x is 1 to 5. Anexample of a family of multiple-silicon atom-containing organofluorosilanes has the formula: R₁((R₂)Si(L))_(n)Si(R₃) where R₁═(H) or(C_(x)F_(2x+1)), R₂═(H)₂ or (C_(x)F_(2x+1))(H), R₃═(H)₃ or(C_(x)F_(2x+1))(H)₂, L=—(O)— or —(C(R₄)₂)_(m)—, n=0 to 5, x=0 to 5, m=1to 4, and each R₄ is independently F or (C_(x)F_(2x+1)). While n canrange from 1 to 6, n preferably ranges from 1 to 4, more preferablyranges from 1 to 3, most preferably ranges from 1 to 2, and typicallyis 1. Also, m can range from 1 to 4, and preferably ranges from 1 to 3,more preferably ranges from 1 to 2, and typically is 1. An example of afamily of cyclic organofluoro silanes has the formula:((C_(x)F_(2x+1))_(p)Si(H)_(2−p)(L))_(q) where L=—(O)— or —(C(R)₂)_(r),each R is independently F or (C_(x)F₂₊₁), p=1 to 2, q=3 to 6, r 1 to 4,and x=1 to 5. While q can range from 3 to 6, q preferably ranges from 4to 5, and typically is 4. As with m above, r can range from 1 to 4, andpreferably ranges from 1 to 3, more preferably ranges from 1 to 2, andtypically is 1.

[0033] Alternatively, a carbon and fluorine-containing silicon-bondedmoiety can contain one or more aromatic rings, so long as it alsocontains at least one carbon atom bonded to a fluorine atom. In one suchcase, the carbon atom bonded to the fluorine atom is an aliphaticcarbon. For example, carbon-containing moieties having one or morearomatic rings can include —Ph—CF₃, —CF₂—Ph, —CF₂—Ph—CF₃, and the like,where Ph is a six carbon aromatic ring. Since aromatic C—H bonds aremore resistant to oxidation relative to aliphatic C—H bonds, thearomatic C—H bond will not be readily oxidized by the oxidizing agentused in the method of the invention. Similarly, an organofluoro silanemay contain an aromatic moiety bound to silicon, which aromatic moietydoes not contain fluorine atoms, so long as the aromatic moiety containsno aliphatic hydrogens, and at least one other silicon-bonded moiety ofthe organofluoro silane contains at least one carbon atom bonded to atleast one fluorine atom.

[0034] Moieties Linking Si Atoms

[0035] An organofluoro silane used in the method of the inventioncontains at least one silicon atom, but can contain up to 6 siliconatoms. Organofluoro silanes containing more than one silicon atom,including cyclic organofluoro silanes, will have either an oxygen atomor a —(C(R)₂)_(r)— moiety (where each R is independently F or(C_(x)F_(2x+1)); r=1 to 4; and x=1 to 5) linking the two or more siliconatoms. It is within the scope of the invention that an organofluorosilane containing three or more silicon atoms may have an oxygen atomlinking a first set of two silicon atoms and a —(C(R)₂)_(r)— moietylinking a second set of two silicon atoms; however, an organofluorosilane will typically contain only oxygen atoms linking silicon atoms oronly —(C(R)₂)_(r)— moieties linking silicon atoms. Preferably,—(C(R)₂)_(r)— is CF₂.

[0036] In one embodiment, it is desirable that some carbon atoms beincorporated into the backbone of the polymer to enhance the thermalconductivity of the resultant dielectric film. Thus a silicon oxidecontaining carbon and fluorine atoms and may have the structure:

[0037] where one or more carbon atoms are incorporated into thesilicon/oxygen chain. Such materials can be formed, for example, usingorganofluoro silanes having a —CF₂— linking two silicon atoms. Forexample, the organofluoro silane used to form the material of structureI can be H₂CF₃SiCF₂SiCF₃H₂.

[0038] Oxidizing Agent

[0039] The oxidizing agent used in the method of the invention can beany oxygen-containing compound capable of reacting with an organofluorosilane to form a Si—O bond. Typically, the oxidizing agent will becapable of reacting with a Si—H bond in forming the Si—O bond. Exemplaryoxidizing agents capable of such a reaction include hydrogen peroxide,oxygen, ozone, and oxides of nitrogen (N₂O, NO, NO₂). Preferably, theoxidizing agent selectively cleaves Si—H bonds in preference overcleaving Si—C bonds, Si—O bonds, or C—F bonds. In one embodiment, theoxidizing agent also selectively cleaves Si—H bonds in preference overcleaving aromatic C—H bonds.

[0040] In another embodiment, an oxidizing agent for use in the methodof the invention is a mild oxidizing agent, for example, hydrogenperoxide. A mild oxidizing agent reactant preferably comprises avaporous source of peroxide. Such a peroxide can be convenientlyobtained by flash evaporation of concentrated (30 vol. % or more) liquidhydrogen peroxide. By the term “source of peroxide” is meant anymaterial capable of being heated (such as liquid hydrogen peroxide), ordecomposed and heated (such as calcium peroxide or barium peroxide), toprovide a vaporous hydrogen peroxide (H₂O₂) oxidizing agent.

[0041] In yet another embodiment, the oxidizing agent is more reactivethan hydrogen peroxide, for example, ozone.

[0042] Reaction Conditions

[0043] The organofluoro silane and the oxidizing agent can be reactedtogether by introducing them into a reaction chamber and carrying outchemical vapor deposition. For example, an organofluoro silane andhydrogen peroxide are introduced into a reaction chamber containing acooled substrate support therein on which is mounted a semiconductorsubstrate such as a silicon substrate on which the reaction product willdeposit. For such a reaction, the reaction chamber is advantageouslymaintained at a pressure of from about 0.1 Torr to about 50 Torr,preferably from about 1 Torr to about 10 Torr, and most preferably fromabout 1 Torr to about 5 Torr. Both the organofluoro silane and thehydrogen peroxide are introduced into the chamber in a gaseous orvaporous phase. The delivery system for the reactants is preferablymaintained at a temperature which ensures delivery of the reactants intothe chamber as gases or vapors, typically from about 70° C. to about100° C. Flow rates of the individual reactants will depend upon chambersize and will also vary with the particular reactants. During thereaction and deposition, the temperature of the substrate support in thereaction chamber is maintained at a low temperature not exceeding about25° C., preferably not exceeding about 10° C., and most preferably notexceeding about 5° C. The reaction and deposition is carried out for aperiod of time sufficient to form the layer of low k fluorine andcarbon-containing silicon oxide dielectric material to the desiredthickness over the integrated circuit structure already formed on thesilicon substrate. Usually this thickness will range from a minimum ofabout 300 nm to ensure sufficient electrical insulation betweenunderlying conductive regions and conductive regions to be formed overthe low k dielectric material up to a maximum of about 800 nm or more.Thicker layers can be formed, but are deemed unnecessary and merely addto the bulk of the structure. Such a reaction method forms a low k filmhaving excellent via-filling properties, yields a dielectric layer withlow adhesion stress, and can be preferable when using silane compoundsthat, under particular conditions, can be oxidized by mild oxidizingagents such as peroxide.

[0044] In another embodiment, the organofluoro silane and oxidizingagent reactants can be reacted together by introducing gaseous orvaporous organofluoro silane or an organofluoro silane-containingmixture and a strong oxidizing agent into a chamber at about 40 Torr toabout 1000 Torr, preferably from about 700 Torr to about 800 Torr. Thereaction can then be carried out at a temperature from about 250° C. toabout 450° C., preferably from about 250° C. to about 400° C., andtypically about 350° C. The strong oxidizing reagent used in thereaction can be any oxygen-containing oxidizing reagent capable ofreacting with an organofluoro silane to form a low k fluorine andcarbon-containing silicon oxide dielectric material, such as ozone (O₃),oxygen (O₂), oxides of nitrogen (N₂O, NO, NO₂), and the like. Thereaction and deposition is carried out for a period of time sufficientto form the layer of low k fluorine and carbon-containing silicon oxidedielectric material to the desired thickness over the integrated circuitstructure already formed on the silicon substrate. Usually thisthickness will range from a minimum of about 300 nm to ensure sufficientelectrical insulation between underlying conductive regions andconductive regions to be formed over the low k dielectric material up toa maximum of about 800 nm or more.

[0045] In yet another embodiment, a plasma-enhanced chemical vapordeposition (PECVD) can be carried out. A plasma-activated strongoxidizing agent and a gaseous or vaporous organofluoro silane or anorganofluoro silane-containing mixture and a carrier gas such as heliumcan be introduced into a chamber at about 1 Torr to about 40 Torr,preferably from about 5 Torr to about 20 Torr. The reaction can then becarried out at a temperature from about 50° C. to about 450° C.,preferably from about 200° C. to about 300° C., and typically about 250°C. The strong oxidizing reagent used in the reaction can be anyoxygen-containing oxidizing reagent capable of reacting with anorganofluoro silane to form a low k fluorine and carbon-containingsilicon oxide dielectric material, such as ozone (O₃), oxygen (O₂),oxides of nitrogen (N₂O, NO, NO₂), and the like. Typically, the strongoxidizing agent will be oxygen. The reaction and deposition is carriedout for a period of time sufficient to form the layer of low k fluorineand carbon-containing silicon oxide dielectric material to the desiredthickness over the integrated circuit structure already formed on thesilicon substrate. Usually this thickness will range from a minimum ofabout 300 nm to ensure sufficient electrical insulation betweenunderlying conductive regions and conductive regions to be formed overthe low k dielectric material up to a maximum of about 800 nm or more.

[0046] While not intending to be limited to the following theory, it isthought that, as the polymer forms, bonds of the organofluoro moietiesto the silicon atoms of the silicon oxide polymer will not be oxidizedas readily as bonds of unsubstituted alkyl moieties to the silicon atomsof the silicon oxide polymer. Furthermore, the dielectric constant ofthe resulting dielectric material having fluorocarbon groups substitutedfor alkyl groups should not be adversely affected by the higherpolarizability of the fluorocarbon groups because of the higher volumeof the fluorocarbon group over the alkyl group, since the dielectricconstant is obtained by dividing the polarizability (α) by the volume(v) in the formula k=α/v and increases in polarizability tend to becanceled out by increases in volume.

[0047] Silane Mixtures

[0048] While the product of the process of the invention principallycomprises a low dielectric constant (low k) silicon oxide dielectricmaterial containing organofluoro groups, it is within the scope of theinvention to utilize, in the process of the invention, mixtures of theorganofluoro silanes with non-fluoro silanes, including SiH₄. In oneembodiment, it may be desirable to use as one component of the mixturean organofluoro silane containing aliphatic C—H bonds. Such materialscan be blended with one or more of the above-described organofluorosilanes to enhance other physical properties of the resultant film oflow k dielectric material. Exemplary physical properties includedielectric constant, adhesion capabilities, via filling capabilities,surface stress, and the like.

[0049] For example, to enhance the film forming properties of the lowdielectric constant fluorine and carbon-containing silicon oxidedielectric material of the invention, one or more organofluoro silanescan be blended with one or more of the following non-fluoro silanes:

[0050] a) silanes having no silicon atoms bonded to carbon-containinggroups;

[0051] b) organo silanes containing silicon atoms bonded to one or morecarbon-containing groups having aliphatic C—H bonds (such as methylsilane used in the Trikon Flowfill process);

[0052] c) organo silanes that do not contain aliphatic C—H bonds, suchas organo silanes containing a silicon atom bonded to an aromatic carbongroup; and

[0053] d) mixtures of any two or more of a), b), and c).

[0054] Such a mixture of silanes which includes one or more organofluorosilanes may be reacted, for example, with hydrogen peroxide (H₂O₂) informing a low k fluorine and carbon-containing silicon oxide dielectricmaterial. For example, a mixture of silanes corresponding to mixture a)above could contain a mixture of silane (SiH₄) and an organofluorosilane having the formula (H)_(y)Si(C_(x)F_(2x+1))_(4−y), where y rangesfrom 1 to 3, x is an integer from 1 to 5. A mixture of silanescorresponding to mixture b) could contain methyl silane combined withthe organofluoro silane (H)_(y)Si(C_(x)F_(2x+1))_(4−y). To form amixture including both a) and b), one could use both silane and methylsilane in combination with the organofluoro silane having the formula(H)_(y)Si(C_(x)F_(2x+1))_(4−y). Other examples of substituted silaneswhich can be used either singly or in combination to form mixtures ofsilanes containing organofluoro silanes include dimethyl silane, ethylsilane, isopropyl (1-methylethyl) silane, n-butyl silane, isobutyl(2-methyl propyl) silane, phenyl silane, and methylenebis-silane.

[0055] As stated above, the amount of such silanes which may be combinedwith one or more organofluoro silanes in the method of the inventionwill typically be combined as minor components. By use of the term“minor component” is meant that the one or more non-fluorosilanes usedin a mixture of silanes will comprise less than 50 volume % of the totalvolume of the compounds in the mixture, ensuring that the majorcomponent of the mixture comprises one or more organofluoro silanes.However, it is recognized that in some instances the enhancement ofother properties of the resulting mixture, e.g., the film formingproperties, may justify the use of more that 50 volume % of othersilanes, that is, up to about 70 volume % of other silanes and 30 volume% of one or more organofluoro silanes, even though such usage may raisethe dielectric constant of the resulting dielectric material.

[0056] When using such mixtures the average dielectric constant of thedielectric material formed using a mixture of silanes can be determinedfor the particular proportions of such dielectric materials using theformula:

k_(av)=Σ_(i)x_(i)k_(i)

[0057] where x_(i) is the volume fraction of dielectric component i andk_(i) is the dielectric constant of the pure dielectric component. Thus,for example, dielectric materials (a) and (b) might be added to the lowdielectric constant fluorine and carbon-containing silicon oxidedielectric material of the invention to enhance the film formingproperties of the resulting mixture. If a mixture is formed comprising10 volume % of dielectric material (a), 15 volume % of dielectricmaterial (b), and 75 volume % of the low dielectric constant fluorineand carbon-containing silicon oxide dielectric material, the averagedielectric constant of the mixture will comprise the sum of the productsof the dielectric constant of each of the materials times its volume %in the mixture. If the dielectric constant of the low dielectricconstant fluorine and carbon-containing silicon oxide dielectricmaterial is 2.4, the dielectric constant of dielectric material (a) is3.5, and the dielectric constant of dielectric material (b) is 3.4, theaverage dielectric constant k_(av) would equal(2.4×75)+(3.5×0.10)+(3.4×0.15)=2.7.

[0058] In Combination with Other Layers

[0059] While the low k fluorine and carbon-containing silicon oxidedielectric material formed in the method of the invention will haveincreased oxidation resistance relative to carbon-doped silicon oxidedielectric material, it may be desirable to form a thin conventional(standard k) silicon oxide (SiO₂) or silicon nitride base layer over thesubstrate to act as a moisture barrier layer for such low k fluorine andcarbon-containing silicon oxide dielectric material subsequently formedthereon. A similar moisture barrier layer may also be formed over such alow k fluorine and carbon-containing silicon oxide dielectric layer forthe same reasons. Such a barrier layer adjacent the layer of low kfluorine and carbon-containing silicon oxide dielectric material can beformed to a thickness of about 50 nanometers (nm) to provide adequateprotection (if deemed necessary) for the low k fluorine andcarbon-containing silicon oxide dielectric layer to be formed thereon.Thicknesses exceeding this minimum may be used, but are probablyunnecessary and may negatively contribute to an undesired rise in theoverall dielectric constant of the resulting composite layer. Suchbarrier layers may then serve to protect the low k dielectric materialduring subsequent processing steps.

[0060] Similarly, the low k fluorine and carbon-containing silicon oxidedielectric material formed in the method of the invention may findutility, for example, as one or more of the low k dielectric layersdescribed in Ser. Nos. 09/425,552; 09/346,493; 09/426,056; 09/426,061;09/605,380; 09/607,512; 09/704,164; 09/704,200; all assigned to theassignee of this invention.

[0061] Product—Dielectric Material

[0062] The low dielectric constant fluorine and carbon-containingsilicon oxide dielectric material produced by the method of theinvention will be suitable for use in integrated circuit structures.This fluorine and carbon-containing silicon oxide dielectric materialwill contain silicon atoms bonded to oxygen atoms, silicon atoms bondedto carbon atoms, and carbon atoms bonded to fluorine atoms. In oneembodiment of the invention, the fluorine and carbon-containing siliconoxide dielectric material will be characterized by the absence ofaliphatic C—H bonds. A fluorine and carbon-containing silicon oxidedielectric material produced by the method of the invention will have adielectric constant below the dielectric constant of silicon oxide orsilicon nitride. Preferably, the dielectric constant of the fluorine andcarbon-containing silicon oxide dielectric material will be below about3.5, more preferably below about 3.

[0063] Additionally, the fluorine and carbon-containing silicon oxidedielectric material will demonstrate superior resistance to degradationin subsequent processing steps such as, for example, via etch andphotoresist removal steps. While not wishing to be limited by aparticular theory, it is considered that organofluoro compounds,particularly those that do not contain aliphatic C—H bonds, will have anincreased resistance to oxidation. This resistance will decrease thesusceptibility of the fluorine and carbon-containing silicon oxidedielectric material to physical degradation which can occur in a varietyof manners, such as thermal instability, solvent absorption, and thelike.

[0064] In one embodiment, the fluorine and carbon-containing siliconoxide dielectric material will contain as principal components onlysilicon atoms, carbon atoms, fluorine atoms, and oxygen atoms. Such afluorine and carbon-containing silicon oxide dielectric material willnot contain a significant number of hydrogen atoms, and, consequently,will not contain a significant number of bonds susceptible to oxidationduring deposition or subsequent processing steps.

[0065] In another embodiment, the fluorine and carbon-containing siliconoxide dielectric material will have a ratio of carbon atoms to siliconatoms of C:Si greater than about 1:3. As described above, theintroduction of carbon atoms into a dielectric material has been usefulfor lowering the dielectric constant of silicon oxide dielectricmaterials. By introducing a greater ratio of carbon atoms to siliconatoms, the dielectric constant can be lowered even further. A particularchoice of C:Si ratio will depend not only upon the desired dielectricconstant, but also upon other desired physical properties of thedielectric material. Thus, a desired C:Si ratio can be greater thanabout 2:3, greater than about 1:1 or greater than about 3:2.

[0066] Similarly, because several components can be combined in a silanemixture used to form the fluorine and carbon-containing silicon oxidedielectric material, some silicon atoms may not be bonded to any carbonatoms, while some carbon atoms may be bonded solely to other carbonatoms and other fluorine atoms. For example, a silane mixture cancontain SiH₄ and H₃Si(CF₂CF₃); in this example, the ratio of C:Si willbe a function of the ratio of H₃Si(CF₂CF₃): SiH₄ in the silane mixture.Such a ratio will typically be greater than about 1:3, greater thanabout 2:3, greater than about 1:1, or greater than about 3:2.Regardless, such a dielectric material will be characterized by thepresence of C—C bonds.

[0067] Thus, the invention provides a low temperature process forforming a low k fluorine and carbon-containing silicon oxide dielectricmaterial exhibiting superior resistance to oxidation than conventionalcarbon-doped low k silicon oxide dielectric materials while alsoproviding good gap-filling capabilities and low stress adhesion notalways found in other fluorine and carbon-containing silicon oxidedielectric materials.

[0068] The following example serves to further illustrate the process ofthe invention.

EXAMPLE

[0069] Trifluoromethyl silane (CF₃SiH₃) and hydrogen peroxide can beintroduced into a reaction chamber containing a cooled substrate supporttherein on which is mounted a silicon substrate on which the reactionproduct will deposit. The reaction chamber is advantageously maintainedat a pressure of about 1-5 Torr. Both the trifluoromethyl silane and thehydrogen peroxide are introduced into the chamber in a gaseous orvaporous phase. The delivery system for the reactants is maintained atabout 100° C., which ensures delivery of the reactants into the chamberas gases or vapors. Flow rates of the individual reactants will dependupon chamber size and will also vary with the particular reactants.During the reaction and deposition, the temperature of the substratesupport in the reaction chamber is maintained at a low temperature ofabout 0-10° C. The reaction and deposition is carried out for a periodof time sufficient to form the layer of low k fluorine andcarbon-containing silicon oxide dielectric material to the desiredthickness over the integrated circuit structure already formed on thesilicon substrate. Usually this thickness will be a minimum of about 300nm to ensure sufficient electrical insulation between underlyingconductive regions and conductive regions to be formed over the low kdielectric material. Such a reaction method forms a low k film havingexcellent via-filling properties, yields a dielectric layer with lowadhesion stress.

[0070] While a specific embodiment of the process of the invention hasbeen illustrated and described for carrying out the invention,modifications and changes of the apparatus, parameters, materials, etc.used in the process will become apparent to those skilled in the art,and it is intended to cover in the appended claims all suchmodifications and changes which come within the scope of the invention.

Having thus described the invention, what is claimed is:
 1. A processfor forming a low k fluorine and carbon-containing silicon oxidedielectric material comprising reacting with an oxidizing agent one ormore silanes including one or more organofluoro silanes characterized bythe absence of aliphatic C—H bonds.
 2. The process of claim 1 whereinsaid oxidizing agent is a mild oxidizing agent.
 3. The process of claim2 wherein said mild oxidizing agent is hydrogen peroxide (H₂O₂).
 4. Theoxidizing agent of claim 1 wherein said oxidizing agent is more reactivethan hydrogen peroxide.
 5. The process of claim 1 wherein said oxidizingagent is selected from the group consisting of ozone (O₃), oxygen (O₂),oxides of nitrogen (N₂O, NO, NO₂), and mixtures thereof.
 6. The processof claim 1, wherein said one or more organofluoro silanes has theformula: (H)_(y)Si(C_(x)F_(2x+1))_(4−y), where y=1 to 3 and x=1 to
 5. 7.The process of claim 6 wherein said one or more organofluoro silanes hasthe formula: (H)₃Si(CF_(m))(CF₃)_(n) where m=0 to 3, and n=3−m.
 8. Theprocess of claim 1 herein said one or more organofluoro silanes has theformula: R₁((R₂)Si(L))_(n)Si(R₃) where R₁═(H) or (C_(x)F_(2x+1)),R₂═(H)₂ or (C_(x)F_(2x+1))(H), R₃═(H)₃ or (C_(x)F_(2x+1))(H)₂, L=—(O)—or —(C(R₄)₂)_(m)—, n=0 to 5, x=1 to 5, m=1 to 4, and each R₄ isindependently F or (C_(x)F_(2x+1)).
 9. The process of claim 8 wherein nis at least
 1. 10. The process of claim 9 wherein said one or moreorganofluoro silanes has the formula: (R₄)Si(CF₂)Si(R₅) where R₄═(H)₃ or(CF₃)(H)₂ and R₅═(H)₃ or (CF₃) (H)₂.
 11. The process of claim 1 whereinsaid one or more organofluoro silanes has the formula:((C_(x)F_(2x+1))_(p)Si(H)_(2−p)(L))_(q) where L=—(O)— or —(C(R)₂)_(r)—;each R is independently F or (C_(x)F_(2x+1)), p=1 to 2, q=3 to 6, r=1 to4, and x=1 to
 5. 12. The process of claim 1 wherein said one or moreorganofluoro silanes are characterized by the presence of Si—H bonds.13. The process of claim 1 wherein said one or more silanes furtherinclude SiH₄.
 14. The process of claim 1 wherein said one or moreorganofluoro silanes include CF₃SiH₃.
 15. The process of claim 1 whereinsaid reacting is carried out at low temperature.
 16. A process forforming a low k fluorine and carbon-containing silicon oxide dielectricmaterial comprising reacting with a mild oxidizing agent one or moresilanes including one or more organofluoro silanes characterized by theabsence of aliphatic C—H bonds.
 17. The process of claim 16 wherein saidone or more silanes consist essentially of one or more organofluorosilanes.
 18. The process of claim 16 wherein said mild oxidizing agentis hydrogen peroxide.
 19. The process of claim 16 wherein said one ormore organofluoro silanes include trifluorosilane (CF₃SiH₃).
 20. Theprocess of claim 16 wherein said reacting is carried out at lowtemperature.
 21. A low dielectric constant fluorine andcarbon-containing silicon oxide dielectric material for use in anintegrated circuit structure comprising silicon atoms bonded to oxygenatoms, silicon atoms bonded to carbon atoms, and carbon atoms bonded tofluorine atoms, wherein said dielectric material is characterized by theabsence of aliphatic C—H bonds and wherein said dielectric material hasa ratio of carbon atoms to silicon atoms of C:Si greater than about 1:3.22. The dielectric material of claim 21 further characterized by thepresence of C—C bonds.
 23. The dielectric material of claim 21consisting essentially of silicon atoms, carbon atoms, fluorine atoms,and oxygen atoms.